China's securities regulator has warned listed companies against flooding the markets with shares after the country's main stock index slumped to a seven-month low.

'Refinancing by listed companies is an important function of the capital market ... but it should never become raking in money maliciously,' said a spokesman from the Chinese Securities Regulatory Commission late Monday.

'Listed firms should, in light of the market conditions and their capital needs, carefully consider the size and timing of refinancing and the capacity of investors,' the spokesman said in a statement on the agency's website.

China's stock market has plunged about 20 per cent this year, partially on concerns about massive share sale plans by listed companies including Ping An Insurance and Shanghai Pudong Development Bank.

The key index lost 4.07 per cent on Monday to 4,192.53, the lowest closing level since July 20, as investors worried whether the market is able to absorb huge supplies of new equity.

The index ended down 18.15 points or 0.43 per cent at 4,174.38 Tuesday morning.

The agency said it would strictly review refinancing plans after taking into account market conditions, noting that it would examine Ping An's share sale plan 'according to regulation' after it is submitted to the agency.